Tires New and used

What's wrong with used tires? Problems with rubber.

May 5, 2016 – 04:17 am

When money is tight, you might be tempted to buy used tires instead of new ones. They can be much cheaper and might even look practically new. But we recommend against it. After all, you don’t really know the history of that used rubber. And because tires affect your car’s safety, we don’t think it’s worth the risk to save a few bucks. What could go wrong? Here are some concerns.

Misuse. If a tire was driven while it was underinflated or overloaded, which is very common, it may have sustained internal damage that’s not visible to the naked eye.

Defects that aren’t obvious. Most consumers probably aren’t skilled enough to detect problems that a tire expert would spot immediately, such as a torn mounting bead, probably caused by removing the tire from the wheel, or badly executed repairs.

Unknown effects of aging. Tire compounds degrade over time. Some automakers recommend against installing tires that are 6 years or older. And some tire makers recommend replacing any tire that’s 10 years or older. Because you can’t see how aging weakens the tire’s internal structure, an older tire, whether or not it has been used, shouldn’t be trusted. You can check a tire’s date of manufacture by looking at the DOT serial number embossed on the sidewall. The last four digits are the date code; the first two are the week, the last two are the year. A code of 3312 means the 33rd week of 2012.

Mismatch. For the best handling—and the safest—you want your tires to match each other in tread pattern, construction, age, wear, and so forth. It’s not a great idea to put on a replacement tire that doesn’t match the one on the opposite side.

Bias-ply tires (also called cross ply tires) are a common design for tires used on vehicles such as automobiles and trucks. All common tires (since at least the 1960s) are made of layers of rubber and cords of polyester, steel, and/or other textile materials. The major difference between bias-ply tires and the other common design, radial tire...